Atlanta Braves outfielder Justin Upton hits a home run off New York Mets relief pitcher Jeremy Hefner during the first inning Monday in Port St. Lucie, Fla.

LAKE BUENA VISTA, Fla. — Justin Upton is told it has to be about the coolest thing in the world to play big-league baseball with his brother B.J.

But he redirects that line of inquiry.

Sure, it was great to join the Braves with his brother, but now it’s time to work.

“It’s fun,” Upton said, “but we’re in ‘baseball mode’ now. We are going about our business the same way we would if we weren’t on the same team.”

That’s why conversations between the brothers in the clubhouse and on the field tend to be technical talk, not familial banter. At a recent batting practice, for example, B.J. was explaining to Justin how he’d worked out a hitch he once had in his swing.

Braves outfielder Jason Heyward said the Uptons have gone out of their way to become integrated with other players rather than stand apart as brothers.

“They are brothers, but you almost forget they are brothers until you think about it,” Heyward said. “They are teammates first. That’s what’s awesome, man.”

The baseball part is nothing new for the Uptons. They are experienced big-league players and so know the rhythms of spring training and how to get ready for the games that count.

What’s new for the Uptons is playing in the same team together. That hasn’t happened since high school, when they teamed up on a fall travel squad.

It’s a rare thing for brothers to make the majors and rarer still for them to play on the same team. The Baseball Almanac estimates it’s happened about 100 other times in history.

“It’s pretty fun,” B.J. said. “It’s been a pretty cool experience so far. I’m sure it’s going to get better during the season.”

The uniqueness of the Uptons’ situation has drawn attention this spring. More relevant to Atlanta’s success is how quickly it takes for the brothers to become comfortable with their new club.

Neither player has had to do it before. Justin spent all of his previous five full seasons with Arizona before the Braves acquired him in a trade in January; B.J. had only played for Tampa since his 2004 debut.

The Braves need them both to adjust quickly. Justin, the left fielder, is slotted to bat third and B.J., the center fielder, is fifth in the order.

“It’s been a good transition,” Justin said. “It’s a good clubhouse, a lot of good guys. Obviously it’s a little bit different for me. I’m getting used to it. I think having a good clubhouse with good guys has helped.”

Atlanta’s mainstays have done their part to help with the process. That’s especially true for Heyward, who plays right field, Justin’s position with the Diamondbacks.

To that end, the three outfielders have spent time away from the field getting to know one another. That’s included time during the spring at B.J.’s home in Tampa.

Braves manager Fredi Gonzalez has aided the process by purposely putting the Uptons and Heyward in the lineup together, which means they also have the same off days.

“These guys have been nothing but great to us,” B.J. said. “They’ve taken us in like one of their own. We have fun. It’s like we’ve been here for years.”

At the same time the Uptons adjust to their new club they are preparing for a season with big expectations for both them and the Braves.

Justin, 25, posted a .785 OPS last season, his lowest since becoming a regular, while struggling with nagging injuries. Arizona management decided the former MVP candidate was expendable.

“I’m trying to get feet my wet with the ballclub and also get back to form and the way I’ve played in the past,” he said. “Obviously last year wasn’t fun dealing with injury and not playing as well. But this year I’m looking to bounce back and just put together a good year.”

B.J., 28, also is trying to duplicate the kind of production he had in earlier seasons that hinted at his potential. His best season was in 2007, when he had an OPS of .894, and he hasn’t approached that mark since then.

“I’m working on things ... ,” he said. “That’s what spring training is for. It’s important than you are working and trying to get ready for the season.”

When word leaked that the Braves were talking to the Diamondbacks about acquiring Justin Upton, B.J. posted a message to his Twitter account that said it would be a “dream come true” if the trade happened.

It did happen. But now that the novelty has faded the Uptons say they are focused on business.

“Yeah, I think it’s cool, but I think we are kind of past that,” B.J. said. “We are just here to play baseball.”